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Low noise amplifier with adjustable gain

An amplifier and noise technology, applied in the field of gain-adjustable and low-noise amplifiers, can solve problems such as difficult precise control and noise performance deterioration, and achieve the effects of improving reverse isolation, reducing harmonic interference, and increasing output impedance

Inactive Publication Date: 2011-05-04
东南大学无锡分校
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  • Application Information

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Problems solved by technology

This method is essentially to control the transconductance of the input tube, or to control the transconductance of the amplifier tube. It is easy to implement, and the gain flatness will not deteriorate when the gain changes, but the noise performance will deteriorate, and it is difficult to control accurately

Method used

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  • Low noise amplifier with adjustable gain
  • Low noise amplifier with adjustable gain

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Embodiment Construction

[0015] The following describes the technical solution of the present invention in detail through a best embodiment in conjunction with the accompanying drawings, but the protection scope of the present invention is not limited to the embodiment.

[0016] The gain-adjustable low-noise amplifier of the present invention applies the basic idea of ​​a Gilbert unit to realize a variable-gain amplifier to a low-noise amplifier, crosses and connects two sets of cascode transistors on the main body cascode transistors, and The current amplified by the catheter is cross-shunted, part of the positive current of the RF input flows to the negative output terminal, and part of the negative current of the RF input flows to the positive output terminal, thereby cross-cancelling to realize the gain adjustment of the low-noise amplifier.

[0017] Such as figure 1 As shown, the gain-adjustable low-noise amplifier of the present invention includes an input amplification stage, a gain control cir...

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Abstract

The invention discloses a low noise amplifier with adjustable gain. The low noise amplifier provided by the invention is characterized in that two groups of cascode tubes are crossed and connected in parallel on a main body cascode tube; the amplified current of a transitron is crossed and shunted; partial radio frequency (RF) input positive current flows to a negative output end; and partial RF input negative current flows to a positive output end, thus a gain control circuit which can adjust the gain of the low noise amplifier is formed through crossed cancellation. Compared with the traditional method for controlling the gain of the low noise amplifier, the low noise amplifier with adjustable gain has the characteristics that the system noises is not increased when the gain is adjusted, the gain control is accurate, the bias and input impedance are not influenced, and the power consumption is not increased.

Description

technical field [0001] The invention relates to a gain-adjustable low-noise amplifier. Background technique [0002] The gain control mechanism is widely used in modern communication systems. Through gain control, the circuit can expand the dynamic range of the received signal, reduce power consumption and improve linearity. Especially in recent years, the rapid development of the portable RF terminal market has made power consumption an increasingly important consideration. The existence of signal attenuation and reflection causes the change of the signal power at the front end of the receiver, and the range of the input signal of the receiver can reach more than 80dB, such as from a small signal of a few microvolts to a large signal of tens of millivolts, low noise As the first stage circuit of the radio frequency receiving system, the amplifier LNA should have the ability to accept and process radio frequency signals with a large dynamic range. The controllable gain can...

Claims

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Application Information

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IPC IPC(8): H03F1/26
Inventor 吴建辉竺磊陈超李红张萌杨世铎徐震赵亮
Owner 东南大学无锡分校
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